Polyethylene Glycol (Peg) Is A Cause Of Anaphylaxis To The Pfizer/Biontech Mrna Covid-19 Vaccine

On the first day of the UK vaccination campaign with the coronavirus disease 2019 (COVID-19) vaccine there were reports of 2 cases of anaphylaxis within minutes of administration of the Pfizer/BioNTech messenger RNA (mRNA) vaccine and a third case of an allergic reaction not requiring adrenaline (epinephrine). This was alarming, as anaphylaxis to vaccines is rare; in the order of 1 case per million doses (1), and therefore likely to injure public confidence. The UK Medicines and Healthcare products Regulatory Agency (MHRA) issued precautionary advice restricting access to the vaccine (2), which was subsequently relaxed in line with the Summary of Product Characteristics. The cause of these vaccine anaphylaxis cases is unclear, but polyethylene glycol (PEG) is a candidate allergen (3,4). Here we demonstrate for the first time that allergy to PEG can cause anaphylaxis to the Pfizer/BioNTech vaccine.